Genetically predisposed individuals, who make up about 10% of the population, become hypersensitized (allergic) to antigens from a variety of environmental sources to which they are exposed. Those antigens that can induce immediate and/or delayed types of hypersensitivity are known as allergens. (King, T. P., Adv. Immunol. 23 77-105 (1976) Anaphylaxis or atopy, which includes the symptoms of hay fever, asthma, and hives, is one form of immediate allergy. It can be caused by a variety of atopic allergens, such as products of grasses, trees, weeds, animal dander, insects, food, drugs and chemicals.
The antibodies involved in atopic allergy belong primarily to the IgE class of immunoglobulins. IgE bonds to mast cells and basophils. Upon combination of a specific allergen with IgE bound to mast cells or basophils, the IgE may be cross-linked on the cell surface, resulting in the physiological effects of IgE-antigen interaction. These physiological effects include the release of, among other substances, histamine, serotonin, heparin, a chemotactic factor for eosinophilic leukocytes and/or the leukotrienes, C4, D4 and E4, which cause prolonged constriction of bronchial smooth muscle cells (Hood, L. E. et al. Immunology, 2nd ed.) The Benjamin/Cumming Publishing Co., Inc., (1984). These released substances are the mediators which result in allergic symptoms caused by a combination of IgE with a specific allergen.
Through them, the effects of an allergen are manifested. Such effects may be systematic or local in nature, depending on the route by which the antigen entered the body and the pattern of deposition of IgE on mast cells or basophils. Local manifestations generally occur in epithelial surfaces at the location at which the allergen entered the body. Systemic effects can include anaphylaxis (anaphylactic shock), which is the result of an IgE-basophil response to circulating (intravascular) antigen.
Allergens constitute the most abundant proteins of grass pollen, which is the major cause of allergic disease in temperate climates (Marsh (1975) Allergens and the genetics of allergy; in M. Sela (ed), The Antigens, Vol. 3, pp 271-359, Academic Press Inc., London, New York)., Hill et al. (1979) Medical Journal of Australia 1, 426-429). The first descriptions of the allergenic proteins in ryegrass showed that they are immunochemically distinct, and are known as groups I, II, III and IV (Johnson and March (1965) Nature, 206, 935-; and Johnson and Marsh (1966) Immunochemistry 3, 91-100). Using the International Union of Immunological Societies' (IUIS) nomenclature, these allergens are designated Lol p Ib, Lol p II, Lol p III and Lol p IV. However, the allergenic spectrum of ryegrass pollen is now known to be more complex. The international reference preparation for ryegrass contains 17 allergens ranging in molecular weight from 12 to 89 kD (Stewart et al. (1988) Int. Arch. Allergy Appl. Immunol. 86: 9-18). These allergenic proteins in pollen have been detected by their ability to bind IgE, the immunoglobulin specifically present in allergic individuals.
Among these allergens, Lol p I, II, III and IV have been extensively studied. The full amino acid sequences of Lol pII and III have been reported. This is made possible by using standard biochemical techniques due to the high amount of allergenic proteins in the pollen and the relatively small molecular weight of the proteins. Although the proteins of Lol p I and IV are abundant in the pollen, only partial amino acid sequences had been reported using the same techniques. This is due to the relatively high molecular weight of the proteins. In addition, it is difficult to purify allergens without any cross-contamination and is labor-intensive. Lack of primary sequence and highly purified allergens in sufficient quantity have been the limiting factor in the development of both therapeutic and diagnostic products for the treatment and diagnosis of type I allergies.
Lol p I is defined as an allergen because of its ability to bind to specific IgE in sera of ryegrass-sensitive patients, to act as an antigen in IgG responses and to trigger T-cell responses. The allergenic properties have been assessed by direct skin testing of grass pollen-sensitive patients. The results showed that 84% had a skin sensitivity to Lol pI (Freidhoff et al., (1986) J. Allergy Clin. Immunol. 78: 1190-1201), demonstrating the primary importance of this protein as the major allergen. Furthermore, 95% of patients demonstrated to be grass pollen-sensitive possessed specific IgE antibody that bound to Lol pI, as demonstrated by immunoblotting (Ford and Baldo (1986) International Archives of Allergy and Applied Immunology 81: 193-203).
Substantial allergenic cross-reactivity between grass pollens has been demonstrated using an IgE-binding assay, the radioallergo-sorbent test (RAST), for example, as described by Marsh et al. (1970) J. Allergy, 46, 107-121, and Lowenstein (1978) Prog. Allergy, 25, 1-62. (Karger, Basel).
The immunochemical relationship of Lol p I with other grass pollen antigens have been demonstrated using both polyclonal and monoclonal antibodies (e.g. Smart and Knox (1979) International Archives of Allergy and Applied Immunology 62: 173-187; Singh and Knox (1985) International Archives of Allergy and Applied Immunology 78, 300-304). Antibodies have been prepared to both purified proteins and IgE-binding components. These data demonstrate that the major allergen present in pollen of closely related grasses is immunochemically similar to Lol p I (Singh and Knox, supra).